OK, a little more information on the bad sound on the Region 2 Season 2 box set from this board:
http://www.zetaminor.com/roobarb/index.php?showtopic=5350&st=50
Here's a quote from the thread:
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Having had a closer look, yes I think they may be pitch corrected.
The reason you think the sound is dull an lifeless is because the pitch is lower (the correct pitch), something many UK people watching PAL coverted shows never hear. As normal USA PAL conversions run 4% faster and thus have a higher pitch. Pitch correction lowers the sound to how it should sound.
I'm guessing from what you say that the R2 release of season 1 was *not* pitch corrected, so now with season two you're actually hearing the sound (bar glitches) at the proper slightly lower pitch.
Problem solved Watson!
PS. there is a little side effect of pitch correction in that you can occasionally hear little pops in the sound.
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These are the problems I was talking about. There are very noticeable jumps in the music in some episodes, so it seems that Season 2 was indeed pitch corrected, therefore the littlle pops in the sound.
Annoying, but at least the songs haven't been replaced.